1. Field of the Invention
The present invention relates to a judging method and a processing apparatus.
2. Description of the Related Art
In the photolithography process in fabricating a semiconductor device, various kinds of heat treatments such as a heat treatment (pre-baking) performed after a resist solution is applied to a front surface of a semiconductor wafer (hereinafter called xe2x80x9cthe waferxe2x80x9d), a heat treatment (post-exposure baking) after the pattern is exposed, and the like are performed.
The aforementioned heating treatments are usually performed by heat treatment units. As shown in FIG. 13, a heating treatment unit 100 is provided with a thick disk-shaped heating plate 101 for placing a wafer W at a predetermined position thereon to heat it. Support pins 102 for supporting the wafer W are provided at the aforementioned placement position on the heating plate 101, so that the wafer W is prevented from being in direct contact with the heating plate 101 when the wafer W is placed thereat. Hoisting and lowering pins 103 for hoisting and lowering the wafer W when the wafer W is placed at the heating plate 101 are provided under the heating plate 101 so as to penetrate through the heating plate 101.
Since the wafer W needs to be heated uniformly within the wafer W surface, it is important to place the wafer W horizontally at the predetermined position when placing the wafer W on the heating plate 101. Thus, a plurality of guide members 105 having inclined planes 104 facing the placement position of the wafer W are provided on the heating plate 101 so as to surround the aforementioned placement position for the wafer W. According to the above structure, when the wafer W is heated, the wafer W transferred from another treatment unit is supported on the hoisting and lowering pins 103 protruded above the heating plate 101 and waiting in advance, and when the hoisting and lowering pins 103 are lowered, the wafer W is lowered and placed on the support pins 102 on the heating plate 101. When the wafer W is placed thereon, if the wafer W is placed out of the predetermined placement position to some extent, it is guided to the accurate position by the inclined planes 104 of the aforementioned guide members 105 as shown in FIG. 14.
However, when the wafer W is deviated from the placement position to a large extent, for example, when the wafer W is placed in such a manner that it rides on the guide member 105, the wafer W is heat-treated in this state, thus causing a defective product due to poor heating. When larger dust than the support pin 102 adheres to the heating plate 101, the wafer W rides on the dust, and poor heating also occurs.
The occurrence of such a defect is usually found in a detecting step to be performed later. However, since many of the aforementioned defects occur successively, it frequently happens that many defective products have already made when the occurrence of a defect is found in the aforementioned detecting step, and therefore it is desired that the occurrence of the aforementioned defects is detected in the earlier step before the damage becomes too heavy.
It is recognized that when the wafer W is placed at the aforementioned heating plate 101, the wafer W at a low temperature takes the heat, and the temperature of the heating plate is reduced temporarily. When the wafer W is not accurately placed thereat, or for example, when the wafer W is obliquely placed thereat, the distance between the heating plate 101 and the wafer W becomes larger, and heat conduction is reduced, thus making the aforementioned temperature reduction smaller. Thus, it is considered to detect whether or not the wafer W is properly placed by utilizing the change in temperature reduction of the heating plate when the wafer W is placed thereat.
However, on this occasion, when it is determined whether or not the wafer is placed properly, for example, based on the lowest temperature during the time in which the heating plate temperature reduces, the lowest temperature has a wide range of variation. Accordingly, it is desired to improve the reliability.
The present invention is made in view of the aforementioned point, and its object is to provide a method for promptly and accurately judging whether a substrate such as a wafer is accurately placed at a heating plate or not and a processing apparatus capable of carrying out the method in order to reduced the occurrence of the defect of the wafer to a minimum.
In order to attain the aforementioned object, the present invention is a method of judging whether a substrate is accurately placed at a predetermined position when placing the substrate at the predetermined position on a plate to perform heat treatment or cooling treatment therefor, and has the step of setting the aforementioned plate at a predetermined temperature, the step of measuring temperature of the plate at least from a first point of time to a second point of time during which the plate temperature changes, after placing the substrate on said plate, the step of calculating a temperature integrated area I determined by a range enclosed by the measured temperature curve changing in time sequence and a set temperature of the aforementioned plate, and the step of comparing the calculated temperature integrated area I with a threshold value of a temperature integrated area previously set.
According to another aspect of the invention, the present invention is a method of judging whether a substrate is accurately placed at a predetermined position when placing the substrate at the predetermined position on a plate to perform heat treatment or cooling treatment therefor, and has the step of setting the aforementioned plate at a predetermined temperature, the step of measuring temperature of the plate at least from a first point of time to a second point of time during which the plate temperature changes, after placing the substrate on the aforementioned plate, and the step of comparing the measured temperature with threshold values related to standard deviation of the plate temperature in a case in which the substrate is accurately placed.
According to still another aspect of the present invention, the present invention is a method of judging whether a substrate is accurately placed at a predetermined position when placing the substrate at the predetermined position on a plate to perform heat treatment or cooling treatment therefor, and has the step of setting the aforementioned plate at a predetermined temperature, the step of measuring temperature of the plate at least from a first point of time to a second point of time during which the plate temperature changes, after placing the substrate on the aforementioned plate, and the step of comparing a maximum temperature difference from the measured temperature with a previously set threshold value related to standard deviation of a maximum temperature difference of the plate temperature in a case in which the substrate is accurately placed. As the aforementioned measured temperature which is compared, for example, the lowest temperature when the plate temperature is reduced to the lowest as a result of the substrate being placed thereat is proposed in case of heat treatment, and the highest temperature when the plate temperature rises to the highest as a result of the substrate being placed thereat is proposed in case of cooling treatment.
The aforementioned temperature measurement may be performed at a plurality of positions on the plate, and the aforementioned comparing step may be performed for each measurement position. By measuring the temperature at a plurality of positions on the heating plate as this, more reliable judgement as to whether the aforementioned substrate is accurately placed or not can be made.
A processing apparatus of the present invention is, in a processing apparatus having a plate for placing a substrate at a predetermined position thereon to heat or cool the substrate at a predetermined temperature, has a temperature sensor for measuring temperature of the aforementioned plate, and a processor for calculating a temperature integrated area I determined by a range enclosed by a measured temperature curve changing in time sequence and a set temperature of the aforementioned plate, based on the measured result of the plate temperature from a first point of time to a second point of time during which the plate temperature changes, after the substrate is placed at the aforementioned plate, which is measured by the aforementioned temperature sensor, and for comparing the temperature integrated area I with threshold values of a temperature integrated area previously set.
Further, according to another aspect of the invention, a processing apparatus of the present invention is a processing apparatus having a plate for placing a substrate at a predetermined position thereon to heat or cool the substrate at a predetermined temperature, and has a temperature sensor for measuring temperature of the aforementioned plate, and means for comparing measured temperature of the aforementioned temperature sensor with a previously set threshold values related to standard deviation of the plate temperature in a case in which the substrate is accurately placed.
According to the present invention, after the substrate is placed at the plate for heating or cooling, the temperature during a period of time when the temperature of the plate reduces or rises is measured, and the temperature integrated area I enclosed by the measured temperature curve in time sequence and the set temperature of the heating plate is calculated. The temperature integrated area in the case in which the substrate is accurately placed is obtained in advance, and the aforementioned temperature integrated area I is compared with the threshold values being allowable values of the ideal temperature integrated area. As a result of the above, when the temperature integrated area I measured and calculated exceeds the aforementioned threshold values, it can be judged that the substrate is not accurately placed. Accordingly, it can be judged whether or not the substrate is accurately placed at the heating plate and heat-treated properly in the earlier step. As the reference for judgement, the temperature integrated area I is used, thus making it possible to make more reliable judgment without being influenced by an instant temperature change and the like due to other factors as compared with when, for example, the lowest temperature of the heating plate is simply used as the reference.
The threshold values of the aforementioned temperature integrated area may be related to standard deviation of the temperature integrated area in a case in which the substrate is accurately placed at the aforementioned predetermined position. As described above, the data of the temperature integrated area in the case in which the substrate is accurately placed at the aforementioned predetermined position is collected in advance, and, for example, the standard deviation of the data is set as the aforementioned threshold values, whereby the aforementioned data that has to be collected in advance is only the temperature integrate area in the case in which the aforementioned substrate is accurately placed. That is, when the standard deviation is not used, the data in the case in which the substrate is accurately placed and the data in the case in which the substrate is not accurately place has to be collected, and the threshold values have to be determined from both the data, whereby much time and effort are spent in collecting the data. Consequently, according to the present invention, it is sufficient if only one kind of data is collected, thus making it possible to reduce working time and effort of an operator. What is related to the standard deviation is, for example, N "sgr" (N is a real number), and the standard deviations "sgr", 2 "sgr", 3 "sgr" and the like are adopted.